Northern Tool offers the Mr. Heater 18,000-BTU Big Buddy Propane Heater for $107.99. Coupon code "256387" drops the price to $87.99. Opt for in-store pickup to dodge the $14.99 shipping fee. That's the lowest price we could find by $25, although we saw it for $10 less last month. It's designed to heat an area up to 400 square feet. Deal ends December 26.